1. The Field of the Invention
The present invention relates to the fields of distributed computing systems, client-server computing and object-oriented programming. More specifically, the present invention includes a method and apparatus for creating object-oriented software applications for use on a distributed object system.
2. The Relevant Art
Object oriented programming methodologies have received increasing attention over the past several years in response to the increasing tendency for software developed using traditional programming methods to be delivered late and over budget. One problem with traditional programming techniques stems from the emphasis placed on procedural models and "linear" code that often is extremely difficult to design and maintain. Generally, large programs created using traditional methods are "brittle", that is, even small changes to isolated elements of the program can affect all elements of the programming code. Thus, minor changes made to the software in response to user demands can require major redesign and rewriting of the entire program.
Object oriented programming strategies tend to avoid these problems because object methodologies focus on manipulating data rather than procedures; thus providing the programmer with a more intuitive approach to modeling real world problems. In addition objects encapsulate related data and procedures so as to hide that information from the remainder of the program by allowing access to the data and procedures only through the object's interface. Hence changes to the data and/or procedures of the object are relatively isolated from the remainder of the program. This provides code that is more easily maintained as compared to code written using traditional methods, since changes to an object's code do not affect the code in the other objects. In addition, the inherent modular nature of objects allows individual objects to be reused in different programs. Thus, programmers can develop libraries of "tried and true" objects that can be used over and over again in different applications. This increases software reliability while decreasing development time, as reliable programming code may be used repeatedly.
The object metaphor in distributed systems is a useful technique as it separates the object's interface from its implementation; thus allowing software designers to take advantage of the functionalities of various objects available to them without having to worry about the details of the object's implementation. The programmer need only be aware of the object's interface. In addition, object oriented distributed systems allow for multiple implementations of a single interface, which interface may reside on different computing platforms that have been connected through a network. Thus, a programmer working on one machine of a network may make a call to an object about which the programmer has no detailed knowledge with the confidence that at the appropriate time that the remote object will be accessed and return its data so that the programmer's code will function properly. Such a system thus maximizes the inherent advantages of object oriented methodologies by taking full advantage of their modularity and encapsulation.
Attempts to provide such facilities have been made using object oriented distributed systems that are based upon a client-server model, in which object-servers provide interfaces to clients that make requests of the object-servers. Typically in such systems, these servers are objects consisting of data and associated methods. The clients obtain access to the functionalities of the object-servers by executing calls on them, which calls are mediated by the distributed system. When the object-server receives the call it executes the appropriate method and transmits the result back to the object-client. The client and object-server communicate through an Object Request Broker (ORB) which is used to locate the various distributed objects and establish communications therebetween.
Although the advantages to employing object oriented programming methodologies through distributed object systems are significant, there remain major hurdles to their implementation. In general, the goal of implementing the reuse of software during the programming process, even in the context of object programming, is difficult to achieve. Typically, programmers are reluctant to use code about which their understanding is minimal or even nonexistent. This is compounded in distributed object systems as the developer(s) of the code may not be easily reached to provide comments and instruction to the programmer whose task is to develop a new application. Thus, although much useful code may be available to the programmer throughout the distributed object system that programmer may not be able to take full advantage of it, thus being forced to rewrite sections of code that have already been developed.
In addition, the entire process of coding vary large programs is extremely difficult. Programmers must be able to analyze huge amount of complex programming code in order to produce a working application. Object programming poses special challenges in this regard as programmers must be aware of the inheritance structures that the objects of the application contain. Thus, in the development of large object-oriented applications the programmer must become aware of the interrelationships among the objects in the program, which awareness is made more difficult by the large amounts of textual material that must be absorbed and analyzed.
The full promise of object oriented methodologies, especially the advantages afforded by their modularity, have yet to be achieved. In particular, it would be highly desirable to allow programmers and other users the ability to create and install distributed objects in a relatively transparent fashion so that objects created in different programming languages and/or objects residing on different computing platforms can be made available on distributed object systems without extensive re-invention of existing programming code, or placing an undue burden on the user. In addition, distributed object programming would be facilitated by methods and designs that simplify the design and analysis of object relationships in an application. Solutions to both of these problems would facilitate the development of object oriented applications and distributed object applications, by allowing the programmer to focus on the tasks that required real creative effort and minimized repetitive coding and analysis.